Catheter

ABSTRACT

A technique for percutaneous treatment of idiopathic hypertropic subaortic stenosis (IHSS) and hypertrophic cardiomyopathy (HCM). IHSS and HCM are diseases of the heart in which the septum of the left ventricle thickens resulting in reduced ventricular performance. Current treatments involve drug therapy or a medical intervention called an interoperative myotomy/myectomy using the Morrow procedure. The present invention uses laser energy delivered via fiber optics placed percutaneously to irradiate the thickened septum to reduce tissue volume of the septum and enhance left ventricular function.

CROSS REFERENCES TO CO-PENDING APPLICATIONS

This application is related to Serial No. 07/400,701, filed Aug. 30,1989, entitled "Catheter" by the same Assignee of this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention generally relates to treatment of hypertrophiccardiomyopathy (HCM) and idiopathic hypertrophic subaortic stenosis(IHSS), and more particularly, relates to percutaneous treatment of HCMand IHSS using laser ablation.

2. Description of the Prior Art

The symptoms of IHSS and HCM have been known for some time in themedical community. With either disease, an enlargement of the tissue ofthe chamber wall within the heart serves to interfere with normalcardiac function. In addition to the standard treatments for impairedcardiac function, the problem has been addressed surgically. Andrew G.Morrow, M.D., et al. discusses such a surgical approach in "OperativeTreatment in Idiopathic Hypertropic Subaortic Stenosis", CirculationVolume XXXVII, Apr. 1968, pages 589-596. Though the clinical results ofMorrow et al. appear to be promising, they warn that care must beexercised because an effective operation requires that the knife must be"plunged into the septum until it is out of sight, completely.

The problem of performing the cardiomyoplasty is in part resolved byJeffrey M. Isner, M.D., et al., in "Laser Myoplasty for HypertrophicCardiomyopathy", American Journal of Cardiology, Volume 53, 1984, pages1620-1625. Isner et al. teach the accomplishment of the procedure by thetechnique of photoablation using an argon laser. However, the maindifficulty with the techniques of Morrow et al., and Isner et al., isthe requirement to perform a thoractomy. The difficulty of performing athoractomy and the added mortality is well known.

SUMMARY OF THE INVENTION

The present invention overcomes the difficulties in the prior arttreatments for HCM and IHSS by use of a new and novel catheter tophotoablate that tissue which impairs cardiac function. The mostimportant advantage is the use of a percutaneous procedure not requiringa thoractomy. This significantly reduces the cost, time, trauma, andmortality rate of the procedure.

The present invention is a new technique to treat IHSS or HCM using apercutaneous approach obviating the need for the interoperative Morrowprocedure. The invention consists of a method to percutaneously delivera catheter via the femoral artery or vein to the septal wall of the leftventricle. The catheter is fixed to the wall by an automatic fixationdevice after which the laser fiber optic tube is inserted into thecatheter and positioned at the distal end. The fiber optic assembly issecured to a laser and which is activated to irradiate the tissue. Aftersufficient volume reduction is achieved by repeated use of laser energy,the device is removed.

In a typical percutaneous procedure to treat IHSS according to theproposed invention, a catheter assembly consisting of a fiber optictube, an automatic fixation device, a delivery catheter and a guidingcatheter with associated connectors is inserted into the human bodyeither in a retrograde fashion through the femoral artery ortransceptually through the femoral vein. The catheter is affixed to theseptal wall in the hypertrophied region by means of a fixation devicecontained within the catheter. The laser is then energized for a periodof time photocoagulating or ablating the irradiated myocardial tissue.The thermal damage caused by photocoagulation creates a local myocardialinfarction with subsequent reduction in tissue volume. This changedecreases the thickness of the septal wall reducing the outflow trackgradient and restoring more normal left ventricular performance.

In photocoagulation part of the laser energy is absorbed by the tissuedirectly underneath the fiber optic probe and part is scatteredthroughout the tissue, eventually being totally absorbed over a muchgreater area than the diameter of the fiber optic tube. The absorbedenergy raises the temperature of the tissue resulting in a controlledinjury and reduced volume of the affected tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects of the present invention and many of the attendantadvantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, in which like reference numerals designate like partsthroughout the figures thereof and wherein:

FIG. 1 is a plan view of the catheter of the subject invention;

FIG. 2 is a cutaway view of the syringe and the proximal end of theguide wire;

FIG. 3 is a cutaway view of the proximal end of the catheter showingentry of the optical fiber;

FIG. 4 is a cutaway view of the proximal end of the outer sheath;

FIG. 5 is a cutaway view of the distal end;

FIG. 6 is a schematic diagram of the procedure using a retrogradefemoral approach;

FIG. 7 is a cutaway view of the heart during ablation using a retrogradefemoral approach;

FIG. 8 is a schematic diagram of the procedure using a transceptualapproach; and,

FIG. 9 is a cutaway view of the heart during ablation using atransceptual approach.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a technique for the percutaneous treatment ofidiopathic hypertrophic subaortic stenosis (IHSS) and hypertrophiccardiomyopathy (HCM). In IHSS the septal wall near the aortic valvethickens reducing the performance of the left ventricle by partially orcompletely occluding the orifice. In HCM the thickness of the myocardiumincreases to the extent that the chamber size is reduced, therebylimiting stroke volume.

The common treatment for either disease is to surgically reduce thethickness by removing some of the muscle tissue (i.e., performing amyectomy) or reforming the myocardium to improve the shape of the insideof the chamber and increase its volume (i.e., cardiomyoplasty). Thereforming can be done surgically (i.e., myoptomy) or by inducing acontrolled infarct. The present invention provides the apparatus andtechnique for performing these procedures percutaneously using laserenergy.

FIG. 1 is a plan view of catheter 10 of the subject invention. Thepurpose of catheter 10 is to transmit energy from a medical laser to themyocardium to enable performance of the procedure. This transfer may betransarterial or transveneous as described below. The many aspects ofcatheter 10 are to optimally facilitate this purpose.

The laser energy is directed to the tissue from distal tip 12. A moredetailed view of distal tip 12 is found in FIG. 5. Distal tip 12 is heldin position within the ventricle by preformed sigmoidal bend 14 ofguiding sheath 18 and fixation wire 42. Distal metal ring 16 provides aradiopaque indication of the location of distal tip 12. For ease ofgrasping and turning guiding sheath 18, it contains winged member 20 atits proximal end. The distal end of wye 26 frictionally engages theproximal end of guiding sheath 18 during use, but is shown exploded inFIG. 1 to view detail.

Inner catheter 22 runs the entire length of guiding sheath 18. Innercatheter 22 contains the inner lumen through which runs the opticalfiber for transmission of the laser energy and the fixation wire 42.Inner catheter 22 is frictionally coupled via swagging or thermoplastyto metal tubing 24 which runs most of the length of wye 26 and definesthe inner lumen of main branch 28 of wye 26. Syringe 30 frictionallyengages main branch 28 of wye 26.

Secondary branch 32 of wye 26 receives sheath 34 which contains theoptical fiber through which the laser energy is transmitted.

FIG. 2 is a cutaway view of syringe 30. At its most proximal end isthumb knob 36. Depressing thumb knob 36 moves shaft 38 distally whichmoves piston 40 distally. Fixation wire 42, which runs the entire lengthof catheter 10, is fixedly attached to piston 40 and is therefore moveddistally by pressing thumb knob 36. Fixation wire 42 is substantiallystiffer than the inner catheter 22 of catheter 10. The movement of thumbknob 36 (and hence fixation wire 42) in the distal or proximal directionpermits medical personnel to maintain the position of distal tip 12 ofcatheter 10 (see also FIG. 1) and to penetrate the heart tissue forstability (see also FIG. 7).

Rubber seal 44 sealingly engages wall 46 of syringe 30. Configuredstopper 48 guides the movement of shaft 38 for smooth operation. Becausesyringe 30 is airtight, it may be used for resisting inadvertentproximal or distal movement of fixation wire 42.

FIG. 3 is a cutaway view of wye 26. The outer structure is a molded,rigid plastic. It has a main branch 28 into which syringe 30 is insertedand a secondary branch which receives the optical fiber. As explainedabove the main branch contains metal tubing 24 which provides a lumenfor fixation wire 42. Metal tubing 24 has an aperture 50 which ispositioned to receive optical fiber 52. Metal tubing 24 is fixedlyengaged by rigid plastic sleeve 54 which in turn is fixedly engaged bythe main body of wye 26 and its distal end 56. Rigid plastic sleeve 62is frictionally engaged by the proximal end of main branch 28. Syringe30 frictionally engages within the inner diameter of rigid plasticsleeve 62.

Sheath 34 runs the length of secondary branch 32. It provides the lumenfor optical fiber 52. Sheath 34 is sealingly engaged by stopper 58 whichin turn is sealingly engaged by the proximal end of secondary branch 32.The outer diameter of sheath 34 is decreased at point 60 correspondingto the distal end of secondary branch 32. Sheath 34 terminates ataperture 50 of metal tubing 24.

FIG. 4 is a cutaway view of the main body of catheter 10. Guiding sheath18 runs substantially the entire length of catheter 10. Its proximal endis covered by strain relief 64 which is somewhat less flexible thanguiding sheath 18, but not rigid. Guiding sheath 18 terminates at point66 exposing inner catheter 22 which terminates at distal tip 12.Sigmoidal bend 14 and distal metal ring 16 are not shown for clarity,but may be seen in detail in FIG. 5.

FIG. 5 is a cutaway view of the distal end of catheter 10. Distal tip 12has a metallic cylinder 68 which frictionally and adhesively engageswithin inner catheter 22. Metallic cylinder 68 also assists in preciselylocating distal tip 12 under fluoroscopy. Optical fiber 52 is fixedlyattached within the lumen of metallic cylinder 68 which also aids inenergy transfer, in addition to terminating optical fiber 52. Fixationwire 42 may be advanced and retracted in the manner discussed above toassist in fixation of distal tip 12.

Sigmoidal bend 14 of guiding sheath 18 is preformed. Because guidingsheath 18 is substantially less flexible than inner catheter 22,sigmoidal bend 14 greatly aids in placement of distal tip 12 and inmaintaining the desired location. Distal metal ring 16 is placed onsigmoidal bend 14. Because distal metal ring 16 is radioopaque, it isalso helpful in identifying sigmoidal bend 14 during the procedure.

FIG. 6 is a schematic diagram of a percutaneous procedure practicing thepresent invention. Yag laser 70 is preferably a Model YAG-1 manufacturedand sold by Quantronix, Incorporated, although similar products areavailable elsewhere. Energy from YAG laser 70 is transferred via opticalfiber 52 to distal tip 12 placed within left ventricle 104 of heart 102of patient 100. In this embodiment, catheter 10 is inserted into thefemoral arterY and proceeds through the aorta into left ventricle 104via the aortic valve (see also FIG. 7). During operation, the entirecatheter system may be cooled by waterflow in the annular space betweenguiding sheath 18 and inner catheter 22.

FIG. 7 shows an enlarged cutaway view of heart 102 undergoing theprocedure of the present invention. As can be seen, left ventricle 104has had its volume diminished by excessive thickness of septal wall 110(shaded area) resulting in HCM. Furthermore, the enlargement of septalwall 110 at point 108 interferes with emptying of left ventricle 104 byoccluding aortic valve 106 resulting in IHSS.

Catheter 10 has been inserted within the femoral artery as shown in FIG.6 and has been advanced through the aorta into left ventricle 104.Notice sigmoidal bend 14 interacts with the irregular shape within leftventricle 104 to maintain the position of metallic cylinder 68 along theaxis of catheter 10. Extension of fixation wire 42 prevents transversemotion. Ideally metallic cylinder 68 is positioned within 1 mm of thetissue to be irradiated with the laser energy. Distal metal ring 16 aidsin verification of placement using fluoroscopy. Once the exact positionof metallic cylinder 68 is obtained, it is afixed by advancing thumbknob 36 as discussed above.

After correct placement of metallic cylinder 68 is verified, a shortburst of laser energy is issued. Preferably the duration isapproximately 15 seconds and the power is approximately 15 watts. Thisenergy is sufficient to either cut the myocardial tissue and therebyreform it or at least produce a controlled infarct which greatly shrinksthe tissue volume at the infarct area. In this fashion, the myocardiumis reformed to enlarge the chamber volume and alleviate occlusion of theaortic outflow track as described by Morrow.

DESCRIPTION OF THE ALTERNATIVE EMBODIMENT

FIG. 8 shows an alternative approach to the procedure. Each of theelements is as shown in FIG. 6. The major exception is that catheter -0is advanced to heart 102 transveneously. Insertion is preferably madeinto the femoral vein and is advanced to the right side of heart 102.Left ventrical 104 is entered transeptally as shown in FIG. 9.

FIG. 9 is a cutaway and enlarged view of heart 102. It differs from FIG.7 only in that left ventrical 104 is entered transeptally as shown usingprocedures known in the art.

Having thus described the preferred embodiments of the presentinvention, those of skill in the art will be able to readily apply theseteachings to other embodiments within the scope of the claims heretoappended.

We claim:
 1. An apparatus comprising:a. a medical laser; b. an opticalfiber responsively coupled to said medical laser; c. a catheter assemblyhaving an outer sheath defining a first lumen and an inner sheathdefining a second lumen removably located within said first lumen, saidoptical fiber being within said second lumen and engaged to said innersheath for advancing said optical fiber to a position adjacent a humanheart; and, d. means coupled to said optical fiber for maintaining saidcatheter assembly in said position adjacent to said human heart.
 2. Anapparatus according to claim 1 wherein said optical fiber is removablylocated within said second lumen.
 3. An apparatus according to claim 2further comprising a fixation wire movably located within said secondlumen.
 4. An apparatus according to claim 3 wherein said inner sheathhas a proximal end and further comprising a rigid wye having a distalend removably engaged to said proximal end of said inner sheath.
 5. Anapparatus according to claim 4 wherein said rigid wye has a main branchhaving a proximal end.
 6. An apparatus according to claim 5 furthercomprising a syringe wherein said proximal end of said main branch isremovably engaged to said syringe.
 7. An apparatus according to claim 6wherein said syringe has a movable plunger which is attached to aproximal end of said fixation wire.
 8. An apparatus according to claim 7wherein said wye has a secondary branch having a third lumen whichremovably contains a portion of said optical fiber.
 9. A method ofreducing the volume of an enlarged left ventricular septal wall of ahuman heart comprising:a. percutaneously entering a blood vessel with adistal end of a guide catheter; b. advancing said distal end of saidguide catheter until it is positioned adjacent a first position of saidenlarged left ventricular septal wall of said human heart; c. advancinga second catheter having an optical fiber through said guide catheter;d. coupling a proximal end of said optical fiber to an output of amedical laser; and, e. photocoagulating tissue by irradiating said firstposition of said enlarged left ventricular septal wall of said humanheart with laser energy transferred from said medical laser to a distalend of said optical fiber.
 10. A method according to claim 9 furthercomprising:a. repositioning said distal end of said catheter assemblyuntil it is positioned adjacent a second position of said enlarged leftventricular septal wall of said human heart; and, b. irradiating saidsecond position of said enlarged left ventricular septal wall of saidhuman heart with laser energy transferred from said medical laser tosaid distal end of said optical fiber.